1. Field of the Invention
The present invention relates to an apparatus for displaying an electronic document and, more specifically, to an apparatus for displaying an electronic document that allows addition of a handwritten memo to an electronic document and appropriately displays both the electronic document and the handwritten memo, as well as to a method thereof
2. Description of the Related Art
Electronic documents represented by electronic books may fall into the following two types in terms of layout-related characteristics.
One type of the electronic document has a concept of a page or pages, and the layout of characters, images and the like forming a main body of the electronic book is fixed. In this type of document, when the contents of the document are to be enlarged/reduced for display, all the elements are enlarged/reduced with the same magnitude, while the layout of characters and images on a page are maintained. Similarly, the document of this type is always displayed in the same layout even when the size of display area is changed or when it is to be displayed on a different terminal. In the present specification, such a type of electronic document that has the fixed layout as described above will be referred to as a static layout type electronic document.
The second type of the electronic document does not have the concept of a page or pages, as represented by HTML (Hyper Text Markup Language). In this type of electronic document, in accordance with various parameters including size and resolution of a display area, font to be used, character size and line space/letter space, the layout of characters and images forming the main body changes. In the present specification, such a type of electronic document that has the layout non-fixed will be referred to as a dynamic layout type document. Among apparatuses for displaying dynamic layout type electronic documents, some allow change in various parameters such as font, character size, sizes of margins, line space and letter space, and direction of imposition (vertical writing, horizontal writing), as the user prefers, to make the document easier to read.
Among the apparatuses for displaying electronic documents, some allow electronic writing to the document, as well as attachment of a tag.
By way of example, Japanese Patent Application Laid-Open No. (Tokkai) H05-40594 discloses an information processing apparatus that allows attachment of a tag to an electronic document. In this apparatus, it is possible to put a tag at an arbitrary position of each page of the displayed document, and further, it is possible to record any character, figure or image on the tag.
Japanese Patent Application Laid-Open No. (Tokkai) H09-101971 discloses a personal electronic book apparatus configured to store information such as text data, voice, drawings, handwritten characters, signs and the like added by users in user-specific areas. In this apparatus, the data added by a user are each stored in the form of a file, and relation between the files and character strings in the main body is specified, so as to realize writing of the information into the document. In this apparatus, it is also possible to underline some part of the main body.
The techniques disclosed in H05-40594 and H09-101971 do not allow direct addition of a handwritten memo to the main body that is being displayed. Such a function would be convenient. In such a case, generally, a prescribed position on the image plane would be used as a reference position, and the position where the handwritten memo is input would be represented by relative coordinates with respect to the reference position. Use of the relative coordinates enables display of the handwritten memo at the same position as that at the time of input, on the layout when the same page is displayed next time.
If the document is the static layout type document, the above-described method may be applied without any problem when a handwritten memo is directly added to the main body that is being displayed. If the document is the dynamic layout type document, however, there would be a complicated problem, as the display layout of the main body changes dependent on conditions of layout (such as the size of display screen, used font, font size and margin size), and the position or size of display of the handwritten memo cannot uniquely be defined.
Referring to FIG. 1, assume that in a document area 30 of a certain size, a handwritten memo 40 input by a user is displayed together with characters and the like forming the main body of the electronic document. The handwritten memo 40 includes characters “attention!” and arrows and underlines to two character strings 42 (represented by three hatched circles) and 44 (represented by three white circles).
FIG. 2 shows an exemplary display that appears when the electronic document is displayed on a display apparatus having a document area of different width from document area 30, with handwritten memo 40 superposed thereon. Referring to FIG. 2, the document area 32 of this apparatus is wider than document area 30. If the electronic document is of the dynamic layout type, different width means different position of return position (line wrapping) of the letter at the end of a line. In the example shown in FIG. 2, the position of character string 44 is shifted to the right of an upper line. As a result, the arrow to character string 44 included in handwritten memo 40 is off from the originally intended position. Similarly, the display position of the main body is also shifted, so that the characters “attention!” comes to overlap the body text. Specifically, the dynamic layout type document involves a problem that when the size of display screen changes, relation between the handwritten memo and the corresponding main body becomes unclear, resulting in an awkward display.
When the length (vertical width) of the display screen is different, the number of lines that can be displayed on one screen image is also different. As a result, when one same electronic document is displayed successively from the head on two display apparatuses having display screens of different sizes, the portion where the handwritten memo is added would be displayed on different pages counted from the head and on different lines of the displayed page. Therefore, even when the position of the handwritten memo is recorded by specifying the position of the memo as originally written along the vertical direction (for vertical writing, position along the horizontal direction) and the page number where the handwritten memo exists, it is impossible to display the handwritten memo at an appropriate position. The display position of the handwritten memo would be inappropriate on a dynamic layout type electronic document not only when the size of display screen is changed but also when display environment including layout rules such as font type or size, letter space or line space, method of justification, or parameters related to the layout is changed. Similar problem arises when one same electronic document is displayed on different display apparatuses, as the parameters mentioned above generally vary.